Filling systems are used in filling machines to fill beverage containers such as bottles or cans with beverages such as mineral water, fruit juice or beer. To control the filling procedure, such filling systems are fitted with valves mounted in the supply path of the filling material.
It is known as regards the case of the above filling control valve being designed other than a foot valve, that drops of filling material will remain at the walls on the valve discharge side and will drip once the valve has been closed. This dripping arises some time after closing the valve, and as a result dripping may even take place when a beverage container is no longer situated below the filler system""s discharge aperture. This dripping may, on one hand, result in filling inaccuracies. On the other hand, the falling drops will either reach the filling machine floor, or they will soil the filling machine below the filling system. Especially as regards high-calorie beverages, the dripping material provides a nutrient substrate jeopardizing the sterility of the filling procedure. Consequently, frequent cycles of cleaning must be carried out to meet the filling sterility requirements. In general, however, cleaning entails interrupting filling and thus interferes with economical operation of the filling machine.
The state of the art counters the above post-dripping problem by fitting the filling system with devices preventing any remnant drops from falling. Illustratively, the discharge aperture of the filling system is fitted with a sieve. However, such sieves negatively affect the flow of the filling material because they entail undesired eddies that, in turn, may produce foaming of the filling material inside the container. When filling fruit juices, which are especially likely to contain fruit fibers, the use of a sieve is precluded anyway because it would quickly clog.
Another drawback of the known post-drip prevention devices is that the drops may fall despite the use of such devices. While the post-dripping problem is being palliated, namely fewer drops shall contribute to soiling the filling machine, the intrinsic problem on the other hand remains unsolved.
Therefore an objective of the present invention is to create a filling system overcoming the above post-dripping problems.
The basic concept of the invention is not to interfere with the dripping of drops that form on the discharge surface but rather to enhance or to force this dripping of the filling material from the discharge surface. Accordingly, the filling system of the invention includes a post-dripping precluding device that enhances early-dripping of the filling material. The discharge surface shall be understood to be at least the filling system""s inside wall zone running at the discharge side of the filling-material control valve as far as the discharge aperture.
According to the present invention, the post-dripping precluding device assures that after the filling-material control valve moves into its closed position, any drops present will fall at once and, hence, shall reach the beverage container that is still situated below the discharge aperture. All drops will have fallen before the beverage container is removed and, as a result, the filling machine will not be soiled on account of time-delayed dripping.
In further accordance with the present invention, the post-dripping precluding device advantageously assumes the form of a hydrophobic discharge surface of at least the discharge zone on the valve""s discharge side. Because the discharge surface of the invention is hydrophobic, drops are unable to adhere to the discharge surface and instead immediately detach off it as soon as the valve shuts off the supply of filling material. The term xe2x80x9chydrophobicxe2x80x9d is to be construed broadly as denoting that the filling material is repelled by the surface.
In further accordance with the present invention, the discharge surface is preferably made of polytetrafluoroethylene (hereinafter PTFE), which is commonly sold under the trademark TEFLON by E. I. Du Pont de Nemours and Company. PTFE exhibits the desired hydrophobia and, moreover, is economical, unobjectionable with respect to foodstuffs, and also is easily machined. It is also stable still at the temperatures of hot filling and it is insensitive to common cleansing means.
The surface of the discharge zone may be made of PTFE, or a portion of the filling system may be a thick, hollowed body made of PTFE of which the inside surface shall constitute the discharge surface. However, the entire filling system may also consist of PTFE.
The present invention also concerns an alternative to this hydrophobic surface wherein the post-dripping precluding device is a micro-structured discharge surface causing a lotus effect. It is known that appropriate microstructured surfaces will reduce the contact area with liquid drops. Accordingly, this alternative also reduces the adhesion of the filling material to the discharge surface and the filling material will immediately drip off. In this manner there will be effective suppression of time-delayed dripping. All wall zones of the filling system that are in contact with the filling material may be microstructured surfaces in this design as well.
A further advantageous alternative of the post-dripping precluding device is designed to induce vibrations in the filling system""s discharge surface. It is well known that the drops on a surface that is both slanted and vibrating will rapidly drop off it. When the surface is made to vibrate, time-delayed dripping will therefore be precluded.
Advantageously and in accordance with another aspect of the invention, the post-dripping precluding device is in the form of mechanical means impacting the filling system. Such means, for instance in the form of a displaceable lever, can be initiated in a synchronized manner, such as by the closing of the valve. As regards rotary filling machines, however, the impacting means also may be a stationary component with which the rotary filling system will periodically collide during rotation.
Alternatively, the post-dripping precluding device applies acoustic waves to at least the filling system""s discharge zone. Therefore, an appropriate sound source must be mounted with acoustic access to the filling system""s discharge zone. The acoustic source may be operated as needed continuously or be timed into operation upon valve closure.
In accordance with a further advantageous alternative, the post-dripping precluding device is in the form of a piezoelectric surface driven into vibrations of voltage-controlled amplitude and frequency. The voltage must, therefore, be appropriately selected. Again, in this embodiment only the surface need be piezoelectric, or else a solid portion of the filling system of which the inside surface shall constitute the discharge surface.
In further accordance with the present invention, the post-dripping precluding device is designed such that an expelling gas may be forced onto the discharge surface. For that purpose the filling system illustratively is fitted with an annular gas-expelling aperture directly underneath the valve seat. The aperture transmits the expelled air into the discharge zone and onto the discharge surface. Any generated drops will be blown away by the expelled air.
Another feature of the invention provides a perforation in the discharge surface and directs a blow-off gas through the perforations into the discharge zone. The discharge surface may advantageously consist of a porous sintered material.